Positioning system, computer-implemented positioning method, computer program and non-volatile data carrier

A computer-implemented method performed in at least one processor (615) of a positioning system, the method comprising:

• receiving, via at least one transmission line, identity and timing information from at least three base stations (B1, B2, B3) in a set of base stations arranged to receive radio messages (M1) from mobile units (U1), each of is the mobile units being carried by a respective entity in a set of entities, each of the mobile units repeatedly transmitting a radio message (M1) including the identity information, wherein the entities move in an area (A), and wherein the base stations forward the identity and timing information;
• determining, based on the identity and timing information, a respective position in the area (A) of each of the entities in the set of entities;
• registering, during a measurement period (TM), respective said positions of the entities in the set of entities in the form of a respective trace (TR1) for each of the mobile units (U1), wherein each said trace is a movement pattern represented by consecutive updates of a respective said entity's position;
• determining whether an alarm criterion is fulfilled, wherein the alarm criterion is fulfilled if, during the measurement period (TM):
• a first predefined number (ITH) of the traces (TR1) are interrupted during a first threshold interval (TTH), and
• the predefined number (ITH) of the traces (TR1) are interrupted in a first zone (Z1) of the area (A), wherein the first zone exceeds a first threshold size (ATH);
• and
• if the alarm criterion is fulfilled, generating a capacity alarm (CA(Z1)) with respect to the first zone (Z1).